System and method for power control in MIMO systems

ABSTRACT

The return channel in a multiple-input and multiple-output (MIMO) communication system is used to provide signal information on an individual-channel basis. In one embodiment, in a controlled factory environment, this information may be used to incrementing up or down the variable gain amplifier and/or the power amplifier of a MIMO transmitter and/or receiver so as to generate a default signal power offset to be used during normal operation. Thereafter, such signal information may similarly be provided via the return channel and used to further adjust the transmit parameters to account for location-specific signal conditions.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of prior application Ser. No.12/351,701, filed Jan. 9, 2009. Applicants hereby incorporate byreference the entirety of prior application Ser. No. 12/351,701.

FIELD OF THE INVENTION

The present invention relates in general to controlling and/or adjustingthe transmit power for each channel in a multiple-input andmultiple-output (MIMO) communication system.

BACKGROUND

Multiple-input and multiple-output systems, or MIMO systems, rely on theuse of multiple antennas on both the transmitter-side as well as thereceiver-side. MIMO technology is increasingly being adopted fornumerous wireless communication applications since such technology tendsto increase data throughput and link range without requiring additionaltransmit power over non-MIMO configurations. In particular, MIMO systemstend to have higher spectral efficiency, as well as improved linkreliability by reducing fading effects.

With reference to FIG. 1, in a typical MIMO communication system 100,the transmitter-side 110 is comprised of multiple individualtransmitters (TX₁-TX_(n)), each having its own antenna and relatedsignal-transmission circuitry (as is generally known in the art). Thereceiver-side 120 is comprised of multiple receivers (RX₁-RX_(n)) eachalso having its own antenna and related signal-receiving circuitry (asis generally known in the art). The MIMO communication system 100 isbased on the concept of sending multiple communication streams using themultiple transmit antennas on the transmitter-side 110. Thesecommunication streams pass through a channel matrix 130, which iscomprised of multiple communications paths extending between the varioustransmit antennas on the transmitter-side 110 and corresponding receiveantennas on the receiver-side 120. The MIMO communication system 100also includes a return channel 140, which is used to provide feedback tothe transmitter-side. Such examples of feedback include: authentication,reception quality and coordinating a frequency jump to a new channel.

Each of the transmitters (TX₁-TX_(n)) typically has its own poweramplifier (PA) and variable gain amplifier (VGA), while each receiver(RX₁-RX_(n)) will have its own VGA. It is not uncommon for one channelto perform better than another, or a certain group of channels toperform better than another group of channels. Ideally, all of thetransmitters (TX₁-TX_(n)) should be very closely matched in outputcharacteristics. In fact, transmitter channels exceeding certain outputtolerances may not satisfy the manufacturer's quality controlrequirements. As such, what is needed is a method for improving theoutput characteristics of MIMO transmitters so as to improve systemperformance and/or reduce manufacturing-related costs.

BRIEF SUMMARY OF THE INVENTION

Disclosed and claimed herein are systems and methods for providing powercontrol in MIMO systems. In one embodiment, a method for providing powercontrol in a MIMO communication system includes measuring a plurality ofsignal strengths provided by a transmitter-side of the MIMOcommunication system, wherein the transmitter-side comprises a pluralityof individual transmitters. This plurality of signal strengths may thenbe correlated to corresponding transmitters of the plurality ofindividual transmitters. The method further includes determining if anyof the plurality of signal strengths exceeds a predetermined tolerance,providing feedback regarding the plurality of signal strengths to thetransmitter-side via a return channel, and then adjusting a signal poweroffset for each of the plurality of individual transmitterscorresponding to any of the plurality of signal strengths that exceedthe predetermined tolerance.

In another embodiment, the aforementioned method may be performed at oneof a user location having an uncontrolled environment, and amanufacturing location having a controlled environment. Additionally,the method may comprise a factory calibration process performed by testequipment, or a power control scheme implemented during normaloperation. In another embodiment, the method may be implemented on thereceiver-side.

Other aspects, features, and techniques of the invention will beapparent to one skilled in the relevant art in view of the followingdetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the present invention willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

FIG. 1 depicts the transmitter-side and receiver-side of a typical MIMOcommunication system;

FIG. 2 depicts a process for implementing a MIMO signal calibrationprocess at the factory-level for the transmitter-side, in accordancewith one embodiment of the invention;

FIG. 3 depicts a process for implementing a MIMO signal calibrationprocess at the factory-level for the receiver-side, in accordance withone embodiment of the invention;

FIG. 4 depicts a process for implementing a MIMO signal calibrationscheme during normal operation, in accordance with one embodiment of theinvention; and

FIG. 5 depicts a block diagram of a MIMO transmitter-side systemconfigured in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Disclosure Overview

One aspect of the disclosure relates to providing feedback in a MIMOcommunication system regarding signal strength information for eachindividual channel. In one embodiment, this feedback may be provided viaa wired or wireless return channel, and may be performed as acalibration process at the factory and/or during normal operation at auser location. When performed at the factory, such feedback informationmay be used to establish default or initial signal power offsets. Whenperformed at a user location during normal operation, such feedback maybe used to account for location-specific interferences and relatedsignal anomalies specific to the user location. In certain embodiments,this process may be performed on a continuous basis while the MIMOcommunication system is in normal operation.

In certain embodiments, the above mentioned feedback may be used tocontrol or calibrate the transmit parameters for each of the individualtransmitters on the MIMO system's transmitter-side. Separate feedbackmay similarly be used to control or calibrate parameters for theindividual receivers on the MIMO system's receiver-side. In oneembodiment, such control may include adjusting the VGA and/or PA offsetsof one or more of the MIMO transmitter and/or receivers comprising theMIMO system. These adjustments, or offsets, may be performed byincrementing up or down the PA and/or VGA by a predetermined amount, oralternatively as a function of the amount by which the measured signalstrength exceeds some tolerance value.

When this calibration process is performed at the factory level, thenumber of devices that exceed the manufacturer's quality controlrequirements for signal output tolerances may be minimized. Theseresulting or default factory-level offsets may then be stored for usewhen the MIMO system (i.e., both transmitter-side and receiver-side) isplaced into normal operation.

Additionally, system-level gain control measures may be employed for theoverall transmitter-side, rather than (or in addition to) on aper-transmitter basis. In certain embodiments, adjusting all signalpower gain levels up or down together may provide better system control,easier signal reception and/or easier demuxing of the transmittedstreams into the original individual streams.

As used herein, the terms “a” or “an” shall mean one or more than one.The term “plurality” shall mean two or more than two. The term “another”is defined as a second or more. The terms “including” and/or “having”are open ended (e.g., comprising). The term “or” as used herein is to beinterpreted as inclusive or meaning any one or any combination.Therefore, “A, B or C” means “any of the following: A; B; C; A and B; Aand C; B and C; A, B and C”. An exception to this definition will occuronly when a combination of elements, functions, steps or acts are insome way inherently mutually exclusive.

Reference throughout this document to “one embodiment”, “certainembodiments”, “an embodiment” or similar term means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the presentinvention. Thus, the appearances of such phrases or in various placesthroughout this specification are not necessarily all referring to thesame embodiment. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner on one or moreembodiments without limitation.

In accordance with the practices of persons skilled in the art ofcomputer programming, the invention is described below with reference tooperations that are performed by a computer system or a like electronicsystem. Such operations are sometimes referred to as beingcomputer-executed. It will be appreciated that operations that aresymbolically represented include the manipulation by a processor, suchas a central processing unit, of electrical signals representing databits and the maintenance of data bits at memory locations, such as insystem memory, as well as other processing of signals. The memorylocations where data bits are maintained are physical locations thathave particular electrical, magnetic, optical, or organic propertiescorresponding to the data bits.

When implemented in software, the elements of the invention areessentially the code segments to perform the necessary tasks. The codesegments can be stored in a processor readable medium or transmitted bya computer data signal. The “processor readable medium” may include anymedium that can store or transfer information. Examples of the processorreadable medium include an electronic circuit, a semiconductor memorydevice, a ROM, a flash memory or other non-volatile memory, a floppydiskette, a CD-ROM, an optical disk, a hard disk, a fiber optic medium,a radio frequency (RF) link, etc.

Exemplary Embodiments

Referring now to FIG. 2, depicted is one embodiment of a process forimplementing a MIMO signal calibration scheme in accordance with theprinciples of the invention. In one embodiment, process 200 may beimplemented as a factory calibration process for the transmitter-side ofsuch a MIMO communication system, such as MIMO communication system 100.In particular, process 200 begins at block 210 where each of the MIMOtransmitters (e.g., TX₁-TX_(n)) may generate a test signal. These testsignals may then be measured at block 220 by dedicated test equipment.In one embodiment, the test signals may be provided to the testequipment via either a wired or wireless channel. When transmittedwirelessly, the test signals may be transmitted in a controlledenvironment so as to minimize ambient interferences andlocation-specific signal anomalies. However, the test signals maysimilarly be provided to the test equipment by each of the individualMIMO transmitters over one or more wired connections. When transmittedover a wired connection, the test signals may be captured at a pointafter the test signal has been generated, but before reaching theantenna. This signal capturing process may be performed by connectingthe test equipment to each of the individual transmitters on thetransmitter-side of the unit under test. It should be appreciated thatthe test equipment may comprise any known equipment capable of receivinga test signal and measuring the signal strength properties thereof(e.g., spectrum analyzer, network analyzer, etc.).

Once the signals have been measured, process 200 may continue to block230 where the measured signal strengths may be correlated to theindividual transmitters that produced them and which comprise thetransmitter-side (e.g., transmitter-side 110) of the MIMO system.Alternatively, the individual transmitters may be correlated to theirrespective signals prior to the measurement operation of block 220.

Process 200 may then continue to block 240 where a determination may bemade as to whether any of the individual transmitters on thetransmitter-side exhibit a signal strength that is outside apredetermined tolerance (e.g., ±X dB) from the other transmitters. Inone embodiment, this tolerance may be set by the manufacturer.

In one embodiment, the determination at block 240 may be made by summingand averaging the signal strengths for all of the transmitters to arriveat a signal average. Then, signal strengths for each of the individualtransmitters may be compared to this computed signal average to see ifany one of the individual transmitters differs from the computed signalaverage by more than a predetermined tolerance (e.g., ±X dB).Alternatively, the determination at block 240 may be based on samplingthe signal strength at block 220 a number of times for each of thetransmitters. These samples may then be compared against standarddeviation values for each of the transmitters.

Still another method for making the determination at block 240 is toagain sample the signal strength at block 220 a number of times for eachof the transmitters. However, instead of directly comparing standarddeviation values, the samples for each transmitter may first be summedand averaged, and then the standard deviation amongst all of thetransmitters may be used to determine if the predetermined tolerance hasbeen exceeded. It should of course be appreciated that numerous otherapproaches for determining whether the signal strength for any of theindividual transmitters exceeds a predetermined tolerance.

Regardless of how the determination at block 240 is performed, if it isdetermined that no individual transmitter is exceeding the predeterminedtolerance, process 200 will continue to block 250 where the process mayend. If, on the other hand, it is determined that any one or more of thetransmitters exceed the signal strength tolerance, then process 200 maycontinue to block 260 where feedback representative of thisdetermination may be provided to the transmitter-side via a returnchannel. Such feedback may be preferably provided by the test equipmentto the transmitter-side via a wired or wireless return channel.

Continuing to refer to FIG. 2, process 200 may then continue to block270 where the transmit parameters may be adjusted up or down for anyindividual transmitter that exceeded the tolerance at block 240. In oneembodiment, such adjustment may comprise adjusting the power offsets(e.g., VGA and/or PA offsets) of the particular transmitter in question.In one embodiment, such calibration may be performed by incrementing upor down the signal power gain by a predetermined amount. Alternatively,the amount of the calibration may be a function of the amount by whichthe given transmitter exceeded the predetermined tolerance. Theoperations of blocks 210-270 may be repeated until the signal strengthsfor each of the individual transmitters have been normalized (i.e., eachexhibit signal strength within tolerance). The final set of resultingsignal power offsets (i.e., adjustments to PA and/or VGA) may then bestored by the particular MIMO system and used as the default signalpower offset when the MIMO system is placed into normal operation.

Referring now to FIG. 3, depicted is another embodiment of a process forimplementing a MIMO signal calibration scheme in accordance with theprinciples of the invention. While process 200 of FIG. 2 above relatesto a factory calibration process for the transmitter-side of such a MIMOcommunication system, process 300 is the corollary factory calibrationprocess for the receiver-side of such a MIMO communication system.

As with process 200 above, the test signals generated at block 310 maybe provided to the test equipment via either a wired or wirelesschannel. When transmitted wirelessly, the test signals may betransmitted in a controlled environment so as to minimize ambientinterferences and location-specific signal anomalies. However, the testsignals may similarly be provided by the test equipment to each of theindividual MIMO receivers over one or more wired connections. Such testequipment may comprise any known equipment capable of producing a testsignal.

Upon being received, these test signals may then be measured at thereceiver-side at block 320. It should be appreciated that any number ofknown means may be used to measure the signal strength.

Once the signals have been measured, process 300 may continue to block330 where the individual measured signal strengths may then becorrelated to the individual receivers that comprise the receiver-side(e.g., receiver-side 120) of the MIMO system.

Process 300 may then continue to block 340 where a determination may bemade as to whether any of the individual receivers indicate a receivedsignal strength that is outside a predetermined tolerance (e.g., ±X dB)from the other receivers. While in one embodiment this tolerance may beset by the manufacturer, it may similarly be based on user preferencesor the like.

As with the determination of block 240 in FIG. 2 above, thedetermination of block 340 may be made using a number of differenttechniques, including each of the techniques described above withreference to block 240. For brevity, the disclosure accompanying block240 above will not be repeated here, but it should be appreciated thatthose same techniques or approaches can apply to the operation of block340.

Regardless of how the determination at block 340 is performed, if it isdetermined that no individual receiver is exceeding the predeterminedtolerance, process 300 will continue to block 350 where the process mayend. If, on the other hand, it is determined that any one or more of thereceivers exceed the received signal strength tolerance, then process300 may continue to block 360 where feedback representative of thereceived signal strength in question may be provided over a returnchannel (wired or wireless) to the test equipment. It should also beappreciated that the determination of block 340 may be performed afterproviding feedback of block 360 to the test equipment. That is, thereceiver-side may provide information signal feedback for each of thereceivers to the test equipment, and then the test equipment can comparesuch signal strength information to known values to determine if thepredetermined tolerance has been exceeded.

Continuing to refer to FIG. 3, process 300 may then continue to block370 where the receive parameters may be adjusted up or down for anyindividual receiver exceeding the tolerance at block 340. In oneembodiment, such adjustment may comprise adjusting the VGA offsets ofthe particular receiver in question. In one embodiment, such calibrationmay be performed by incrementing up or down the gain by a predeterminedamount. Alternatively, the amount of the calibration may be a functionof the amount by which the given receiver exceeded the predeterminedtolerance. The operations of blocks 310-370 may be repeated until thesignal strengths for each of the individual receivers have beennormalized (i.e., each exhibit received signal strength withintolerance).

Referring now to FIG. 4, depicted is a process for implementing a MIMOsignal power control scheme during normal operation, in accordance withone embodiment of the invention. In particular, process 400 may beimplemented in normal operation in an uncontrolled environment, such aswould be the case at a user location. Process 400 may preferably beperformed on a continuous or periodic basis during operation of the MIMOsystem.

Process 400 begins at block 410 with each of the MIMO transmitters(e.g., TX₁-TX_(n)) transmitting a training signal to the receiver-side.In one embodiment, the training signal may comprise a predefined patternor sequence that the receiver-side is expecting or would otherwiserecognize. It should also be appreciated that the training signals maybe transmitted using any previously-stored default signal power offsetsthat were determined above in accordance with processes 200 and/or 300.These training signals may be generated on a continuous or periodicbasis during operation of the MIMO system.

Once received, these training signals may then be measured at block 420on the receiver-side (e.g., receiver-side 120). It should be appreciatedthat any number of known means may be used to measure the signalstrength. Once the signals have been measured, process 400 may continueto block 430 where the measured signal strengths may be correlated tothe individual transmitters that produced them and which comprise thetransmitter-side (e.g., transmitter-side 110) of the MIMO system.Alternatively, the individual transmitters may be correlated to theirrespective signals prior to the measurement operation of block 420.

Process 400 may then continue to block 440 where a determination may bemade as to whether any of the individual transmitters on thetransmitter-side exhibit a signal strength that is outside apredetermined tolerance (e.g., ±X dB) from the other transmitters. Thistolerance may be set by the manufacturer or may be user-defined.

As with the determination of blocks 240 and 340 of FIG. 2 and FIG. 3,respectively, the determination of block 440 may be made using anynumber of different techniques, including each of the techniquesdescribed above with reference to block 240.

Regardless of how the determination at block 440 is performed, if it isdetermined that no individual transmitter is exceeding the predeterminedtolerance, process 400 will follow path 450 and repeat the operations ofblocks 410-440 in a continuous or periodic manner. The time incrementfor repeating blocks 410-440 may be factory-based or user-based.

If, on the other hand, it is determined at block 440 that any one ormore of the transmitters exceed the signal strength tolerance, thenprocess 400 may continue to block 460 where an optional receivercompensation operation may be initiated. In particular, this receivercompensation operation may be initiated at block 460 by determiningwhether the receiver-side is able to compensate for the identifiedout-of-tolerance signal(s) from block 440. If it is determined that thereceiver-side can compensate, process 400 may continue to block 470where such compensation may be performed. In one embodiment, suchcompensation may include adjusting the VGAs of one or more of theindividual receivers comprising the receiver-side. In one embodiment,such compensation may comprise adjusting (e.g., incrementing up or down)the VGA offsets of one or more of the individual receivers on thereceiver-side.

If, on the other hand, it is determined at block 460 that thereceiver-side cannot compensate for the identified out-of-tolerancesignal(s), or if the optional receiver compensation feature is notperformed as part of process 400, then process 400 may then continue toblock 480 where the receiver-side (e.g., receiver-side 120) may providerepresentative feedback over the MIMO system's return channel (e.g.,wireless return channel 140). It should also be appreciated that thedetermination of block 440 may be made on the receiver-side or on thetransmitter-side. If made on the transmitter-side, then the feedbackoperation of block 480 may be performed prior to the determination ofblock 440.

Continuing to refer to FIG. 4, process 400 may then continue to block490 where the transmit parameters may be adjusted up or down for anyindividual transmitter that exceeded the tolerance at block 440. In oneembodiment, this adjustment may comprise adjusting the power offsets(e.g., VGA and/or PA offsets) of the particular transmitter in question.In one embodiment, such calibration may be performed by incrementing upor down the signal power gain by a predetermined amount. Alternatively,the amount of the calibration may be a function of the amount by whichthe given transmitter exceeded the predetermined tolerance. Theoperations of blocks 410-490 may continue in a continuous or periodicmanner while the MIMO system is in operation.

Although not depicted in FIG. 4, in another embodiment a system-levelgain control scheme may be employed for the overall transmitter-siderather than (or in addition to) the individual transmitter adjustmentprocess of FIG. 4. This power gain control scheme may include making adetermination (e.g., at block 440) as to whether the overall signalstrength from the transmitter-side is acceptable (e.g., within a desiredrange, above a minimum level, etc.). This determination may be based onuser preference, the particular communication application, etc.

If it is determined that the overall signal strength is not acceptable,the receiver-side may similarly provide feedback to that effect over theMIMO system's return channel. This feedback may be used on thetransmitter-side to control the transmit parameters applicable acrossall of transmitters. In particular, the transmitter gain for all of thetransmitters on the transmitter-side may be adjusted up or down by thesame amount so as to provide better system control, easier signalreception and/or easier demuxing of the transmitted streams into theoriginal individual streams.

It should further be appreciated that the MIMO system's wireless returnchannel (e.g., return channel 140) is comprised of a single transmitteron the receiver-side, and a single receiver on the transmitter-side. Assuch, the transmitter and receiver that comprise the return channel maysimilarly be calibrated using process 400.

Referring now to FIG. 5, depicted is an exemplary MIMO transmitter-sidesystem 500 configured in accordance with the principles of theinvention. Transmitter-side system 500 includes a plurality ofindividual antennas and related signal-transmission circuitry (e.g.,VGA, PA, etc.), denoted in FIG. 5 as transmitters TX₁-TX_(n). Thedetails of the transmitters' VGAs, PAs and other signal transmissioncircuitry are generally known in the art.

The transmitter-side system 500 further includes power control logic 510for controlling/adjusting the VGA and/or PA of each individualtransmitter TX₁-TX_(n) based on the feedback from return channel 520(which may be wired or wireless) and in accordance with processes 200 or400 of FIG. 2 or 4, respectively. In particular, the power control logic510 may be used to adjust the signal power offsets, as described indetail above. In another embodiment when, for example, the determinationoperations of blocks 240 and/or 440 described above are to be performedon the transmitter-side, such operations may similarly be performed bythe power control logic 510.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention not be limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art. Trademarks and copyrightsreferred to herein are the property of their respective owners.

What is claimed is:
 1. A computer-implemented method for providing powercontrol in a multiple-input and multiple-output (MIMO) communicationsystem, the method comprising the acts of: measuring a plurality ofsignal strengths provided by a transmitter-side of the MIMOcommunication system, wherein the transmitter-side comprises a pluralityof individual transmitters, wherein the measuring the plurality ofsignal strengths comprises sampling the plurality of signal strengths anumber of times to produce a plurality of signal samples for each of theplurality of transmitters; computing a plurality of standard deviationsfor each of the plurality of transmitters based on the plurality ofsignal samples; summing and averaging the plurality of standarddeviations to generate a standard deviation average; comparing thestandard deviation average to a predetermined tolerance; determining ifany of the plurality of transmitters are exceeding the predeterminedtolerance based on the comparing; determining if any of the plurality ofsignal strengths exceeds the predetermined tolerance; adjusting a signalpower offset for each of the plurality of individual transmitterscorresponding to any of the plurality of signal strengths that exceedthe predetermined tolerance; and storing a default signal power offset,based on the adjusting the signal power offset, for use during normaloperation of the MIMO communication system.
 2. The method of claim 1,wherein the method is performed at one of a user location having anuncontrolled environment, and a manufacturing location having acontrolled environment.
 3. The method of claim 1, further comprisingcorrelating the plurality of signal strengths to correspondingtransmitters of the plurality of individual transmitters.
 4. The methodof claim 1, further comprising providing feedback regarding theplurality of signal strengths to the transmitter-side via a returnchannel, wherein the return channel is one of a wired and a wirelesscommunication channel.
 5. The method of claim 1, wherein determining ifany of the plurality of signal strengths exceeds the predeterminedtolerance further comprises: summing and averaging the plurality ofsignal strengths to generate a signal average; comparing the signalaverage to the predetermined tolerance; and determining if any of theplurality of transmitters exceeds the predetermined tolerance based onthe comparing.
 6. The method of claim 5, wherein summing and averagingthe plurality of signal strengths to generate a signal average furthercomprises summing and averaging the signal strengths for all of theplurality of transmitters to arrive at a signal average.
 7. The methodof claim 1, wherein adjusting the signal power offset comprisesadjusting at least one of a variable gain amplifier and a poweramplifier for each of the plurality of individual transmitterscorresponding to any of the plurality of signal strengths that exceedthe predetermined tolerance.
 8. The method of claim 1, wherein adjustingthe signal power offset comprises adjusting the signal power offset by apredetermined increment.
 9. The method of claim 1, wherein adjusting thesignal power offset comprises adjusting the signal power offset based onan amount that a corresponding one of the plurality of signal strengthsexceeds the predetermined tolerance.
 10. The method of claim 1, furthercomprising providing feedback regarding the plurality of signalstrengths to the transmitter-side via a return channel before thedetermining if any of the plurality of signal strengths exceeds thepredetermined tolerance.
 11. The method of claim 1, wherein the methodcomprises a factory calibration method performed by test equipment. 12.A multiple-input and multiple-output (MIMO) communication systemcomprising: a transmitter-side including a plurality of individualtransmitters adapted to transmit signals having a correspondingplurality of signal strengths; and a receiver-side including a pluralityof receivers adapted to receive the signals, wherein the receiver-sideis further adapted to: measure the plurality of signal strengthsreceived from the transmitter-side, wherein the receiver-side is adaptedto measure the plurality of signal strengths by sampling the pluralityof signal strengths a number of times to produce a plurality of signalsamples for each of the plurality of transmitters; wherein at least oneof the transmitter-side and receiver-side is further adapted to: computea plurality of standard deviations for each of the plurality oftransmitters based on the plurality of signal samples; sum and averagethe plurality of standard deviations to generate a standard deviationaverage; compare the standard deviation average to a predeterminedtolerance; determine if any of the plurality of transmitters areexceeding the predetermined tolerance based on the comparison; determineif any of the plurality of signal strengths exceeds the predeterminedtolerance; and adjust a signal power offset for each of the plurality ofindividual transmitters corresponding to any of the plurality of signalstrengths that exceed the predetermined tolerance; and wherein a defaultsignal power offset, based on the adjusted signal power offset, is to beused during normal operation of the MIMO communication system.
 13. TheMIMO communication system of claim 12, wherein the signal power offsetis adjusted at one of a user location having an uncontrolled environmentand a manufacturing location having a controlled environment.
 14. TheMIMO communication system of claim 12, wherein at least one of thetransmitter-side and receiver-side is further adapted to correlate theplurality of signal strengths to corresponding transmitters of theplurality of individual transmitters.
 15. The MIMO communication systemof claim 12, wherein the receiver-side is further adapted to providefeedback regarding the plurality of signal strengths to thetransmitter-side via a return channel of the MIMO communication system,and wherein the return channel is one of a wired and a wirelesscommunication channel.
 16. The MIMO communication system of claim 12,wherein at least one of the transmitter-side and the receiver-side isfurther adapted to: determine if any of the plurality of signalstrengths exceeds the predetermined tolerance by summing and averagingthe plurality of signal strengths to generate a signal average; comparethe signal average to the predetermined tolerance; and determine if anyof the plurality of transmitters exceeds the predetermined tolerancebased on the comparison.
 17. The MIMO communication system of claim 12,wherein at least one of the transmitter-side and the receiver-side isfurther adapted to adjust the signal power offset by adjusting at leastone of a variable gain amplifier and a power amplifier for each of theplurality of individual transmitters corresponding to any of theplurality of signal strengths that exceed the predetermined tolerance.18. The MIMO communication system of claim 12, wherein at least one ofthe transmitter-side and the receiver-side is further adapted to adjustthe signal power offset by a predetermined increment.
 19. The MIMOcommunication system of claim 12, wherein at least one of thetransmitter-side and the receiver-side is further adapted to adjust thesignal power offset based on an amount that a corresponding one of theplurality of signal strengths exceeds the predetermined tolerance. 20.The MIMO communication system of claim 12, wherein the receiver-side isfurther adapted to provide feedback regarding the plurality of signalstrengths to the transmitter-side via a return channel of the MIMOcommunication system prior to at least one of the transmitter-side andthe receiver-side determining if any of the plurality of signalstrengths exceeds the predetermined tolerance.